Mounting Screws for Encoder

We are can’t seem to find what type of screws are used to mount the encoders on to the ToughBox Mini. Can someone point us in the right direction.


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Yup. You won’t need much length if you’re using the E4T encoder (I believe it ships with them in any case). With the SRX encoder, you can get the kit from AndyMark. It has two 1/2" long 3-48’s and a rubber bushing. My local hardware stores only sell 3-48’s in stainless, so don’t give up looking until you check there.

In trying to reduce the steel in the area, I have also mounted encoders to this form factor using brass 4-40 screws, needing a bit more oomph to get them in the first time.

we’re using a different encoder package than the E4T from AM (I forgot exactly what the other mentor ordered).

He measured the clearance hole that he said he uses at 0.0625, which is way smaller than a #3 screw.

I haven’t worked with the encoder area of the gearbox before, so I really can’t say much more than what I heard from him.

To give much more specific help, we’ll need to know what encoder you have. See if you can find the documentation, or a part number, or at least post a photograph of the encoder and (if you still have it) the packaging; someone may recognize it.

What I was told is there are only 2 holes in the toughbox mini for mounting an encoder, so to me it seems that it doesn’t matter what encoder is being used, as long as the screw fits.

I tried looking on AM for a good drawing of the Toughbox mini, but was on my phone and only found an assembly-level drawing.

I’ll check again in our next meeting

I know the E4T is designed to mount directly on the TBmini. Its mounting screw spacing is .586" per this drawing. This agrees with the spacing on the AM encoder mounter for the original TB (which I happen to have within arms reach here at my home PC), and which I am confident match the holes on the TB-mini and TB-micro. The encoder pad originally had holes of 0.075". It was fairly easy to tap with a #3-48 stainless screw, but I was also able to do it more deliberately with a brass #4-40.

TLDR: The encoder mount holes on the TB-mini are 0.586" on center, 0.075" diameter.

Alright I’ll check it out. Thanks!

Update: after mangling the toughbox housing, breaking a few screws, and damaging a bearing shield, we got the encoder mounted with some brass screws for plastic/wood we had laying around (they might be #3).

BTW, the encoder we used was the FC one:

Does anyone have any better suggestions for mounting those in the future?

The closest set of mount holes on the amt103-v are on a 16mm (.630") bolt circle, larger than the TBmini case. The only rigid way to do it would be to drill new holes in the TB-mini case, and tap those. Like the E4T, the screws would need to be short to not damage the bearing. If using wood or sheet metal screws, I would have drilled and tapped the holes without a bearing present, then cut off the screws to a length where it would not hit the bearing before assembly.

Another possibility would be to use adhesives. :man_shrugging:

Yup, that’s exactly what we figured out The AMT103-V has two holes at the right spacing, but those are the ones measured out at ~0.063. Fun fact: we bought some #0 screws. They fit in those holes, but unsurprisingly do not even come close to fitting in the toughbox housing

Also drilling/screwing in is how we damaged the bearing shield – lesson learned.

The whole time I was teasing our other mentor that he should just superglue it… glad to see we’re on the same page =]

I’m trying to add a FC amt103-v to a toughbox mini, and decided to give superglue a chance. The pre-existing holes didn’t seem to be far enough out for the housing.

I used a 3M Scotch-Weld noted for plastic bonding, another FC item IIRC. I also added a dab onto the shaft as a precaution against slipping. You had to be pretty careful about applying too much adhesive to the back plate and there isn’t much clearance between in and the shaft collar. So I tried to not apply any right by the shaft opening. It was still drying earlier so I have longer before deciding if it worked okay or not. There are definitely some potential cons, but I’ll deal later with them if they come up.

E4T mount success: I used 2mm cap-head screws, 4mm long.
The mount plate for E4Ts’ matches the cast holes in the ToughBox case, but those holes are way too small for the screws that come with the E4T. I made a DIY-tap using a long 2mm machine screw, by filing a v-groove using a rat-tail file on opposite sides. After tapping, I used 4mm-long screws on the bottom mount plate, with the spacer tool on the shaft during final tightening.

My mounting efforts were made after the two CIM’s and the TB were attached to the chassis, so space was tight, magnetic fields strong, and the lighting bad. Fortunately, I had an extra-long 2mm ball-end Allen wrench from Harbor Freight, which made it easier to keep the DIY tap vertical, and to tighten the 4mm mounting screws.

I found a nice set of 2mm machine screws on Amazon:

2mm cap-head metric screw set

Just say no to threaded fasteners for mounting those encoders. VHB all the way, quick and easy to install, will stay on as long as you want it to and a thin blade or a twist will remove it when you want it to. The only trick is to apply a piece of tape, with the backing still on, to the bushing tool so that the adapter bushing is moved out the thickness of the tape.